Tractors and utility vehicles used for agriculture, lawn care or recreational use may have a hydrostatic transmission that drives a final drive transmission or range transmission of the vehicle. The final drive transmission or range transmission may drive at least one wheel. The vehicle speed may be operator modulated by changing the drive ratio of the hydrostatic transmission, as well as the range gears. The drive ratio may be changed by moving the angle of a swashplate of a variable displacement pump of the hydrostatic transmission.
Hydrostatic transmissions in tractors and utility vehicles may be operated using foot pedals to control the direction and speed of the vehicle. For example, a first foot pedal may pivot a swash plate in the hydraulic pump to an angular alignment in which hydraulic fluid provided to the hydraulic motors propels the vehicle forward, and a second foot pedal may pivot the swash plate to move the vehicle in reverse. If neither foot pedal is applied, the swash plate may be in a neutral position.
Advantages of hydrostatic transmissions include infinite speed control for a given engine speed, powered creep, and anti-stall control. It is highly desirable for a tractor or utility vehicle to have these operational features that are available in hydrostatic transmissions. However, some operators are not accustomed to hydrostatic transmission controls, and/or prefer using a gear shift to control travel of the tractor or utility vehicle, and others would prefer using only an accelerator pedal like an automatic transmission. A control apparatus is needed for a hydrostatic transmission that can simulate a gear shift, or automatic transmission, to control movement of the tractor or utility vehicle. A transmission control is needed for a hydrostatic transmission that will enable operators to select between different modes of operation.
Additionally, manufacturing costs are higher for tractors or utility vehicles that are produced with several different transmissions available. A transmission control is needed for a hydrostatic transmission that can reduce manufacturing costs by allowing a single transmission to simulate more than one operational mode.